The Rio Grande chub is a small bodied, adaptable fish that lives in streams and lakes throughout the Rio Grande River Basin in Colorado, New Mexico and Texas. Historically, the Rio Grande chub was probably the most common fish in the San Luis and Rio Grande basins, but this species has declined dramatically due to range-wide water diversions, dams and competition and predation from non-native species. The Rio Grande chub is a state threatened species in Colorado and a species of greatest conservation need in New Mexico. It was petitioned for federal listing under the Endangered Species Act in 2013 but currently no listing decision has been made.
The Rio Grande chub evolved as an onmnivore and insectivore as part of a unique fish community in the Rio Grande Basin that included the Rio Grande cutthroat trout (Oncorhynchus clarki virginalis), a piscivore, and the Rio Grande sucker (Catostomus plebius), an algivore. This algivore-piscivore-insectivore assemblage provides balance and allows the survival of the entire fish community because each fish occupies a different niche by using different resources and habitats. These three species composed most of the fish populations in the Rio Grande and San Luis drainages.
Stream habitat loss, fragmentation and degradation from water diversion projects, overgrazing and development have negatively impacted Rio Grande chub populations over the last 100 years. These human-caused activities have degraded aquatic habitats by damagingzones, channelizing streams and increasing sediment and pollution. Water diversion projects also alter stream flows, resulting in increased temperatures and dewatering. The introduction of more than 25 non-native species in the Rio Grande drainage has increased predation of and competition with the Rio Grande chub. Non-native northern pike (Esox lucius), brown trout (Salmo trutta) and brook trout (Salvelinus fontinalis) prey extensively on Rio Grande chubs, while white suckers (Catostomus commersonii) and common carp (Cyrprinus carpio) compete for limited food resources and habitat.
Habitat fragmentation occurs when low head dams, reservoirs, trans-basin water diversions and even improperly designed or undersized culverts create barriers to Rio Grande chub’s movement, especially at low flows typical of the streams they inhabit. They require upstream and downstream movement for genetic exchange, for reproduction and access to suitable habitat as streams throughout their range seasonally flood and then dry up in late summer and fall. Creating and improving fish passage by replacing and retrofitting culverts is an important part of conservation for this species.
Recovery efforts for the Rio Grande chub involve a variety of state, federal, tribal and private organizations. Examples include habitat restoration, improving fish passage, removal of non-native species and reintroductions with individuals raised in hatcheries. Population monitoring throughout their range helps identify changes and patterns. Research on genetics, movement and life history helps us further understand this species and implement more effective conservation and management efforts across its range.
The Rio Grande chub looks a bit like a small trout. Their caudal, or tail fin, is deeply forked with broad pointed lobes. Their mouth is even with their eyes, which are large relative to their heads and is particularly noticeable in smaller fish. Females are typically larger than males.
MeasurementsLength: 9.8 in (250 mm) in lakes; 5 to 6 in (130 to 150 mm) in most streams; 8 to 10 in (200 to 250 mm) in hatcheries
Rio Grande chub have dark coloration on their back, sometimes with two darker stripes on their sides and their undersides are pale silver. They can have yellowish orange coloration where the anal, pelvic and pectoral fins meet the body. During spawning season, this coloration extends across the entire fin, as well as their cheeks and lower body, turning bright orange to crimson with males having brighter more intense color. Males will also develop tubercles, or bumps, on their caudal fins, anal fins and peduncle, or the narrow part of the body before the tail. Juveniles are mostly silver with fine scales and slightly darker dorsally.
Like most species of freshwater fish, Rio Grande suckers begin life as an egg. An embryo develops inside the egg which eventually hatches into a larval fish that can acquire its own food. They grow into juvenile fish sometimes called fry. At this stage they look like small adults and, although their coloration may be different, they have all their normal fins and internal organs. Fish are considered adults when they are reproductively mature. For Rio Grande chubs this occurs after two or three years. If they can avoid predation, they continue to reproduce annually throughout their lives.
Rio Grande chubs can live 15 to 16 years in a hatchery, but in the wild, they likely live around seven years.
Rio Grande chubs reach sexual maturity at 2 to 3 inches (60 to 80 mm) or around two to three years. Growth rates and maturity depend on food resources and temperatures of a given stream. Males and females will school together when they are ready to reproduce, or spawn. Spawning time is influenced by temperatures and spring runoff patterns and can take place between March and June. In streams, they spawn in riffle habitat without building nests and provide no parental care after egg laying. They can also reproduce in lakes. Each year, females can produce 1000 to 4000 ova, or reproductive cells that develop into eggs once they are fertilized in water. Their semi-adhesive eggs then sink to the stream bottom where they stick to gravels.
The Rio Grande chub looks similar to other chub species, but unless they are introduced, no other chub species occupies the same range. Roundtail chub (Gila robusta) live in the adjacent Colorado River drainage and Chihuahua chub (Gila nigrescens) live in the nearby Mimbres drainage, in the southern part of the Rio Grande sucker range, but geographic barriers naturally separate these species. Rio Grande chub can sustain viable populations where it has been introduced, and chubs will readily hybridize. This could cause problems for other native chub species.
The Rio Grande chub thrives both rivers and lakes at elevations up to 11,370 feet. It commonly inhabits pools in cool, fast-flowing stream reaches with gravel or cobble bottoms. Undercut banks and overhanging vegetation provides cover and aquatic insects for food.
A considerable inland body of standing water.
A natural body of running water.
The Rio Grande chub is omnivorous and known to feed on aquatic and terrestrial insects, crustaceans, other small invertebrates, small fish, plankton and some vegetation.
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